Effect of steam cooking and storage time on the formation of resistant starch and functional properties of cassava starch

In this study, resistant starch (RS), type 3, was prepared by debranching, steam cooking and storage of cassava native starch obtained from two Nigeria varieties (TMS 30572 and 98/0581). The native starch samples were debranched with isoamylase enzyme, steam cooked both at atmospheric and high pressure (15 psi) and stored under refrigeration (5-7°C) and freezing condition (−18°C) for 48 h. The effects of these processing conditions on the formation of RS were determined. The debranching process increased the resistant starch contents of the cassava starch to about 70% over the undebranched samples. The RS contents from the steam cooking process ranged between 5.99 and 19.55 g/100 g. The highest value was obtained in TMS 30572 debranched and steam cooked at atmospheric pressure while the least RS was obtained from TMS 98/0581 undebranched but steam cooked at atmospheric pressure. The RS contents increased with increase in storage time with refrigeration having a higher resistant starch contents compared with freezing. Formation of RS decreased the Swelling Power, Water Absorption Index and Water Solubility Index of the Starch while the Syneresis Value increased. This study showed that cassava starch is suitable for isoamylase debranching, and RS formation.